Mid-exhaust steam-engine.



Mu v W m H. LENTZ.

MID-EXHAUST STEAM ENGINE.

APPLICATION FILED SEP'LSO, 1914.

1, 1 1 1 Patented Nov. 24, 1914.

' of another form of valve-gear HE S ATES FFICE HUGO LENTZ, 0F HALENSEE, NEAR BERLIN, GERMANY.

MID-EKHAUST Specification 0 Toallwhomitma concern:

Be it known t at I, Hnoo Learn, a citizen of the German Empire, and residing at Halensee, near Berlin, Germany, have invented certain new and useful Improvements in Mid-Exhaust Steam-Engines, of which the following is a specification.

My invention relates generally to socalled mid-exhaust steam engines, i. c. to steam engines havin exhaust ports which are located in the middle of the cylinder and are controlled by the piston. and particu larly to engines of this type having valvestem guides which are disposed parallel to the cylinder and open into a common casing containing any suitable valve gear for actuating the valves. According to my in vention this valve-gear casing Cflllfitltllitr' part of the exhaust chamber, i. is connected with the same, so that there must be the same fall of pressure between the ends of the valve stems as in the halves of the cylinder located parallel thereto.

An important object of my invention is to provide that the \valve stems can be more readily packed than heretofore and this is possible in my improved arrangement because the pressure at the ends of the guides of the stems is equal to the pressure of the exhaust and is thus so low that the clearances between the ends of the stems and the guides are filled by water of condensation. An additional advantage gained by this arrangement accordingly, a uniform distribution of temperature along the entire cylinder casting, thus not only along the cylinder itself but also along the valve-stem guides cast thereon, whereby stresses in the casting are etfectively obviated.

To these ends my invention consists in the construction, arrangement and combination of parts described hereinafter and pointed out in the claims.

One illustrative embodiment of my invention. and modifications thereof are represented by: way of example in the accom panying drawing. wherein Figure 1 is a longitudinal section through a horizontal mid-exhaust steam engine of the type described, Fig. 2 is a like view of a modified form of valve-gear casing for a horizontal engine, and Fig. 3 is a like view casing for a vertical engine.

Referring to the drawing, a designates the is a constant "fall of pressure and;

STEAM-ENGINE 1 Letters Patent. Patented Nov. 24, 1914.

30. 1914. Serial N0. 864,231.

:tcain cylinder in which the exhaust slots l) are arranged in the middle and thc admis sion ports 1' at the ends. The valve casings (l are connected to lhe latter. These casings or boxes 4/ contain the admission valve '0 which control the admission of the steam to the cylinder. The stems of these valves are gnided'in holes y which are drilled parallel to the cylinder and open approximalcl over the exhaust slots I) into a casing h containing the lay shaft '2' and the cam It. The ends of the valve stems f provided with anti-friction rollers bear against the (am and are driven by the latter against the action of the springs 1. If desired, however. thevalve stems mav be actuated by any other suitable driving device.

The valve-gear casing it constitutes a part ol the annular exhaust chamber at surrounding the exhaust ports I: or is connected with this chamber: consequently, the ends of the valve stems nearest the casing h are subjected to the exhaust pressure, while the ends of the stems remote therefrom are subjected to the full pressure of the steam. Therefore the fall of pressure in the cylinder and in the guides of the valve stems is exactly equal. so that the stems can be readily packed and, in addition, no stresses can he set up in the casting in consequence of its being heated at one end more than at the other. l

The invention can also be applied to such engines in which. for the purpose of lubri' rating the parts of the valve gear welldthe using it is separated by a wall n tromithe exhaust chamber and is partially filled with oil, asshown in Fig. The free space dver the oil is connected by an inserted tube 0 with the exhaust chamber m. The same an rangement can also be employed in a still more simple manner in vertical engines, as shown in Fig. 3. In this case it is only necessary to bore in the wall n a hole p which establishes the connection of the free space above the oil \vitlrtho exhaust chamher. l

1. In a steam engine of the class described. the combination with a cylinder having admission ports at each end, and

central exhaust ports. ot admission valves having stems parallel to thecylimlor. guide casings for the stems. means for actuating the valves in the proper alternation, and means for subjecting the casing ends adjasaid guide casings and the exhaust ports,

a sion ports at each end and central exhaust and means within the casing for actuating the valve stems.

3. In apparatus of the class described the combination with a cylinder having admisports opening into a discharge ccnduit 'a'dmission valves, valve stems parallel to the cylinder and having their free ends in proximity to each other and to a point in the conduit nearythe exhaust ports in the cylinder, guide casings for the stems, a casing inclosing the free ends of the stems and guide casings and communicating with the conduit at said point, and means within the casing for actuating the valve stems; whereby the free ends of the valve stems and guide casings are subjected to substantially the full pressure and temperature of the steam escaping at the exhaust ports of th cylinder.

In testimony whereof, I alfix my signature in the presence of two witnesses.

HUGO Laura Witnesses: 

